function f = yoy_sum(DATA , N)
    if size(DATA , 2) > 1
        error('Must be column vector!')
    end
    T = size(DATA , 1);
    
    sum_matrix = nan(T - 4 * (N - 1) , N);
    for i = 1 : N
        sum_matrix(: , i) = DATA(4 * (i - 1) + 1 : 4 * (i - 1) + T - 4 * (N - 1));
    end
    
    f = sum(sum_matrix , 2);
end